Environmental Hazard: Deforestation – JSS3 Basic Science Lesson Note (First Term)

Deforestation is the clearing of forest trees for farming or other purposes without immediate replanting.

• Cause: it is the indiscriminate cutting down of trees by human activities.
• Result: forest land is lost and the environment is damaged.

Behavioural objectives

1. Define deforestation.
2. State the reasons why people cut down trees.
3. List the effects of deforestation on the environment.
4. Explain afforestation and reforestation as ways of controlling deforestation.
5. State government regulations against deforestation.

What are the key terms in deforestation?

Four terms are used often in this topic.

• Deforestation: clearing of forest trees without immediate replanting.
• Indiscriminate: done without care or control, such as cutting any tree anywhere.
• Timber: wood from felled trees used for building and furniture, such as iroko, mahogany and obeche.
• Arboreal animals: animals that live in trees, such as monkeys and some birds.

Why do people cut down trees?

People cut down trees to get wood and to make room for farms, buildings and roads.

• Timber: trees are felled for woodwork such as doors, tables and roofing.
• Firewood and charcoal: used for cooking and heating at home and in industries.
• Farming: forest land is cleared for crops and grazing.
• Bush burning: fire destroys trees and young plants.
• Urbanisation: towns and cities are extended into forest areas.
• Buildings: trees are cleared for schools, houses, industries, markets, churches and mosques.
• Roads and bridges: trees are removed along the routes.
• Overgrazing: big animals eat grasses and small trees faster than they grow back.

What are the effects of deforestation on the environment?

Deforestation exposes the soil, changes the climate, destroys wildlife and reduces forest products.

Effects on soil and land

• Exposure to wind: forests are wind-breakers, so cleared areas suffer strong winds.
• Soil erosion: bare soil is washed or blown away, which destroys farmland and buildings.
• Loss of water and nutrients: bare soil loses water and nutrients through intense evaporation.
• Desertification: the land may slowly turn into desert.

Effects on the atmosphere and climate

• More carbon(IV) oxide: fewer trees means less carbon(IV) oxide is used in photosynthesis.
• Greenhouse effect: the extra carbon(IV) oxide traps heat in the atmosphere.
• Global warming: a large concentration of carbon(IV) oxide raises the temperature of the Earth.

Effects on plants and animals

• Plant extinction: some species of plants may disappear.
• Animal migration and extinction: arboreal animals lose shelter and food, so they leave or die out.

Effects on people

• Loss of forest resources: resins, bark, fruits, honey, mushrooms and medicinal plants become scarce.
• Scarcity of wood: timber and firewood become hard to get.

How can deforestation be controlled?

Deforestation is controlled by replacing trees, reducing the need for wood and protecting forests.

• Afforestation: planting trees where they have not existed before.
• Reforestation: replanting trees where they were originally present.
• Alternative sources of heat: using gas, kerosene, electricity or solar energy instead of firewood and charcoal.
• Wildlife parks and game reserves: protected areas where trees and animals are kept safe, such as Yankari Game Reserve.
• Modern cattle rearing: ranching and paddocking reduce overgrazing.

What is the difference between afforestation and reforestation?

Afforestation is the planting of trees in an area that has had no forest before.

Reforestation is the replanting of trees in an area where forest was cut down.

What are the government regulations against deforestation?

Forest regulations are rules made by the government to control the destruction of forests.

• Logging restriction: logging is limited, and all loggers must plant trees.
• Heavier penalties: charges and convictions for indiscriminate logging are increased.
• Command and control: public authorities make laws and enforce them with penalties.
• Protected forests: forest areas are protected by law as forest reserves.
• Anti-poaching rules: hunting in reserve areas is prohibited.

Evaluation

1. State four effects of deforestation on the environment.
2. Differentiate between afforestation and reforestation.
3. Mention two ways of controlling deforestation.
4. State two government regulations against deforestation.
5. Explain how deforestation leads to global warming.

Assignment

Answer all the questions below in your exercise book.

1. Cutting down of trees and clearing of forests indiscriminately is called: A. afforestation B. deforestation C. regulation D. conservation
2. Forests provide ………… for wildlife: A. shelter B. poison C. money D. roads
3. ……………… is one of the dangers of deforestation: A. good soil B. good road C. increase in population D. extinction of wildlife
4. A set of rules by the government to control excessive destruction of forestry is known as: A. forest reserve B. forest regulation C. forest destruction D. forest activities
5. All of these are regulations for forestry except: A. practising bush burning B. prohibition of poaching in reserve areas C. enactment of laws against cutting of trees D. establishment of forest game reserve
6. (a) Define deforestation.
   (b) State four reasons why people cut down trees.
7. State three effects of clearing forests on wildlife.